Abstract: Based on the detailed analyses and discussion of petroleum geological conditions of the Xihu Depression,the East China Sea,this paper systematically calculated the potential petroleum resources,resources in leads and total resources,and then established the series and structure of resources and presented the distribution characteristics of discovered and undiscovered resources.The Concept of petroleum resource abundance was introduced to estimate the exploration potential of the Xihu Depression,especially the Baoshu Slope and the Central Anticlinal Belt,by comparing with the resource abundance of the other depressions in East China.